If you had suddenly been blindfolded and transported to Dahlia, a cocktail lounge that opened in May at the Downtown Proper hotel in Los Angeles, you might have asked yourself: Where in the world am I?

The high walls are painted dusty rose, and the booth cushions are upholstered in velvety brown, like the desert floor after rain. Artworks in a terra-cotta palette cover the walls, including a bulbous wicker sculpture that looked somewhat suggestive, like one of Georgia O’Keeffe’s abstract flowers.

There was a sweating glass bottle of Mexican mineral water on a table, along with a small plate of lime wedges so fat and juicy that they seemed otherworldly.

Had you been dropped into a boutique hotel bar in San Miguel de Allende? Sedona? Santa Fe?

The answer might not have become any clearer when Kelly Wearstler, the woman who designed the bar and the hotel, walked through the stained-glass doors. She was dressed in oversize denim from head to the pointed toes of her leather Loewe ankle boots, which had a built-in denim cuff folded over the shaft. When she spoke, it was with a slight Southern twang.

“Oh, can you still hear the accent?” asked Ms. Wearstler, 55, who was born and raised in South Carolina before moving to Massachusetts for college.

Not long after she graduated, she moved to Los Angeles, where she has lived for 30 years. Jobs as a waitress and onetime Playboy model aside, she has spent most of that time designing decadent homes, high-end hotels and idiosyncratic objects to decorate them, like marble sofas, chunky credenzas and lamps covered in spore-like spheres.

She has also become one of the world’s most famous interior designers. She has 2.1 million followers on Instagram, where she often shares her work alongside photos of herself wearing outré clothes. (Riding a public bike in Paris in knee-high Givenchy boots, for instance, or balancing in Loewe’s deflated balloon heels while potting plants in her living room.) Each post has its own magazine-style caption, and some are sponsored.

She judged a Bravo reality show called “Top Design” in the mid-2000s. She has a MasterClass. This summer, she appeared on the covers of Harper’s Bazaar’s Netherlands and Architectural Digest China. Her sixth book, “Synchronicity,” will be published on Sept. 26, and it includes glossy photographs of her hotel projects, among others. Her last book, “Evocative Style,” came out in 2019 and is on Amazon’s list of best-selling interior and home design books.

Lena Wald, a friend of about 20 years and a jewelry designer in Los Angeles, said that when she was recently in Paris with Ms. Wearstler, a group of Korean design students approached her outside the Palais-Royal. They had studied Ms. Wearstler’s work in school.

Ms. Wald, who declined to give her age — “I’m a few years younger than Kelly,” she said — also recalled being stopped by Ms. Wearstler’s fans when they were at the Round Top Antiques Show in Texas. During an interview with Ms. Wearstler in August at the Santa Monica Proper hotel, where she also designed the interiors, two people approached her within 10 minutes to introduce themselves and hand her business cards.

Although Ms. Wearstler has been recognized for her decorating style, it can be hard to define. She likes to combine pieces with dissimilar textures, layering them like a design lasagna. When she first rose to prominence in the 2000s, journalists described the look as Hollywood Regency or maximalist. (Her clients then included the singer Gwen Stefani and the restaurant at Bergdorf Goodman.) The word “eclectic” is often applied to Ms. Wearstler’s work; “that one drives me crazy,” she said.

The Proper hotel in Downtown Los Angeles — a neighborhood that has struggled as the city’s homelessness crisis has accelerated — is a place to eat Iberian-inspired food on Mexican-made furniture. Work by local contemporary artists is mixed with flea-market finds, and upstairs, in homage to the building’s past life as a Y.W.C.A., there is a suite with a private indoor pool stretching beneath a grand ivory ceramic mural. It starts at about $4,800 per night.

In suites like that, about half of the décor is vintage and half is new, a combination that is essential to Ms. Wearstler. “A philosophy of mine is: Old soul, new spirit,” she said. “It’s how I dress. It’s how I design.”

Heart and Soul

Ms. Wearstler uses the word “soul” often.

On a recent tour of the Downtown Proper hotel, which opened in 2021, she said that some walls were given plaster treatment to “feel more soulful.” A mirror shaped like a mushroom “adds so much heart and soul” to a bathroom, she said, compared with a non-mushroom-shaped mirror.

Later, as she climbed into her matte Lamborghini S.U.V. and drove to her nearby storage warehouse, she began to describe her sensibility with another word: “love.”

“Literally everything goes back to love,” Ms. Wearstler said, walking through tall aisles between shelves stuffed with plastic-wrapped and boxed décor she has been collecting for more than 20 years. Some of it she had commissioned, or produced through her studio in West Hollywood. Other pieces were found at antiques malls or bought from galleries around the world.

There was a vintage tapestry from London that she has owned since before her 2002 wedding to Brad Korzen, a founder and the chief executive of the Kor Group, a real-estate-investment firm, and of Proper Hospitality, which operates the Proper hotels. (There are four, all designed by Ms. Wearstler.) There was a mirror with a goopy, puffy metallic frame by the artist Amelia Briggs.

How does Ms. Wearstler choose these pieces? “You just fall in love,” she said. “That’s what design and life is about: Falling in love. That amazing warm feeling that’s in your soul.”

When asked to describe what seemed to be a quintessential Kelly Wearstler piece at her warehouse — a large bronze bowl with nine long cylindrical legs unevenly spaced around its base — she said, “I just love things that have repetition. I like things that have weight and permanence and are sculptural.”

But when it came to defining her style, she resisted labeling it. Instead, she said, “I’m constantly moving forward and pushing myself — I don’t want to repeat myself.”

“As a designer, I’m a free spirit,” she said. “It’s like a moving target.”

Amy Astley, the editor of Architectural Digest, said that it was hard to capture Ms. Wearstler’s aesthetic in a short pithy phrase. “But I do think she’s a master of jolie-laide,” or finding beauty in the unconventional or strange, she said.

The dominant style in American interiors right now, according to Ms. Astley, is “a clean oatmeal look,” which is not quite minimalist but formulaically spare. Living rooms are light and bright with a big statement sofa or coffee table.

Ms. Wearstler uses “weighty, hefty, juicy, meaty kinds of shapes — like in her chairs or in her sofas — and there’s a real masculinity to her work,” Ms. Astley said. “The colors are the opposite of girlie.”

Lately, Ms. Astley said, Ms. Wearstler’s most influential interiors have been designed for places like hotels and with a low-slung 1970s vibe. “It’s slouchy, it’s sexy, it’s relaxed, and it’s cool,” she said.

David Alhadeff, the founder of the Future Perfect gallery, where Ms. Wearstler has acquired contemporary pieces from artists including Eric Roinestad and Chris Wolston, said Ms. Wearstler has a confident eye.

“She buys something because she’s passionate about it,” he said. “She is emotionally drawn toward the work.”

On ‘Synchronicity’

In recent years, Ms. Wearstler has taken on a number of unconventional projects, like designing a techno brutalist-meets-midcentury-modern garage for an electric Hummer ad.

Her more conventional endeavors have included designing a full tabletop collection — her first — in collaboration with Serax, a Belgian décor brand, which was released in August.

At her studio, where she has about 50 employees, she is working on the conversion of the former Cal Neva Lodge and Casino in Lake Tahoe into the next Proper hotel. Cal Neva was once owned by Frank Sinatra.

“We’re going to make it sexy and cool,” Ms. Wearstler said of the casino floor. Such spaces, she added, are generally “not cool.” There will be game tables, but no slot machines, she said: “It will be something like you would see in Monaco.”

Toward the end of last year, Ms. Wearstler began looking into artificial intelligence after the release of ChatGPT’s public chatbot. A handful of her employees are working on how to incorporate A.I. into the studio’s work.

So far, it’s a brainstorming tool. On a Friday afternoon in August, Tulika Lokapur, an interior designer at Ms. Wearstler’s studio, showed how the technology is being used. Ms. Lokapur prompted a chatbot to “imagine a library with blackened steel shelving in Lake Tahoe,” then uploaded two images to guide the A.I. toward the right style.

Ms. Wearstler compared using A.I. to having a junior designer scour old design books for inspiration — like a new team member pitching ideas.

“You’re still being creative,” said Ms. Wearstler, who is aware that there is pushback to using A.I. in creative fields. “You still have to know design history and style. It’s very important, because how are you prompting if you don’t?”

Ms. Lokapur, 33, said, “We’re also very cautious of how we’re using it and the message that we’re sending with it.”

This future feels far from Ms. Wearstler’s beginnings, which she described as modest. She went to the Massachusetts College of Art and Design to study graphic design, after developing a passion for collecting old fashion magazines as a teenager. “Myrtle Beach is not a cultural place,” she said of her hometown in South Carolina. “It was my escape.”

At college, she became fascinated while watching a “cute guy” build 3-D models in an open studio one day, she said. She began taking architecture classes, and decided to “meet in the middle and do interior design,” as she put it.

She then took an apprenticeship in New York with the designer Milton Glaser, of “I ♥ New York” fame, but found herself drawn to Los Angeles, in part for its proximity to the ocean. Her first interior design job came when a friend introduced her to a couple who wanted help with their Venice bungalow. She filled it with vintage furniture she found at the Rose Bowl and other markets.

At the time, she was working as a waitress. Within about three years of decorating that Venice house, she had started an interior-design studio and stopped working in restaurants to run it full-time.

Home Life

At the start of her career, Ms. Wearstler said, work was her priority, over having children. But while engaged to Mr. Korzen, she became pregnant with her oldest son, Oliver, now 21. Soon after, they had second son, Elliott, now 20. Though both pregnancies were difficult, she said, she loved having a family. Years later, she still wanted another baby.

“Probably 30 to 40 percent of our friends had gotten divorced and remarried, and they were having kids,” she said. “Why can’t we do it?”

“I feel, like, 20 years old,” she added.

The couple’s third son, Crosby, was born by surrogate last September. They learned their surrogate’s water had broken while Ms. Wearstler was hosting a pool party at their home in Beverly Hills, a palatial estate built in 1926 that she refers to as the Broccoli house. (It is nicknamed for its previous occupant, Albert Broccoli, a producer of James Bond films.)

It was about seven weeks before Crosby’s due date. “We freaked out,” Ms. Wearstler said. They slipped out of the party and drove to a hospital outside Santa Barbara.

At that point, they had told only a small number of family members and friends about their choice to have Crosby, who was born two weeks later.

“You want to keep it private, and then when the baby comes, you celebrate,” Ms. Wearstler said, citing other women in their 50s who have chosen surrogacy, like the supermodel Naomi Campbell. “It’s been like a rebirth for our family.”

Ms. Wearstler hosts a play group twice a week at her home for babies and their mothers or nannies, most of them women in their 30s. Some are the younger second wives of men who already have children the same age as Ms. Wearstler’s older sons. “I’m the anomaly,” she said. “But I’m fine with it.”

Though the manicured mansion is the family’s main residence, they occasionally rent it out for brand events. During the Oscars, Versace removed some of Ms. Wearstler’s modern furniture to display several archival couture gowns. The magazine Racquet has hosted a party on the sunken tennis court.

While the home is opulent — there is a glass-enclosed Padel court and marijuana- and oregano-scented Loewe hand soap stocked in a bathroom — it also feels like a place where people live. And eat: Ms. Wearstler, who grazed on a snack platter she had prepared on a Saturday afternoon in August, seemed to have expanded her diet since telling Bon Appétit in a 2013 interview that, with the exception of dinner, she mostly drank juice all day.

That weekend, she and Mr. Korzen, 59, swam and hung out at home with their many boys: Oliver and Elliott, both students at the University of Texas at Austin, who were preparing to return to campus; Crosby, fussy after a nap; and the family’s two rescue dogs, Javier and the distinctive Willie, who, with more than 12,000 Instagram followers, has also achieved a modicum of fame.

Call it the Kelly Wearstler effect. As her friend Ms. Wald put it: “She’s more of a celebrity now — not just a designer.”